1. Identifying Variables & Designing Investigations

2. Independent Variable The thing that is changed by the scientist
The thing being tested or manipulated
Also called manipulated variable
Always plotted on the “X” axis of a graph
Remember:
“I” change the independent variable

3. Dependent Variable
The thing that might be affected by the change in the independent variable. The RESPONSE to the thing that you change.
What is observed and/or measured
The data collected during the investigation
Also called the RESPONDING variable
Plotted on the Y axis

4. Constants All the things that are not changed in an experiment
Allow for a “fair test”
You should only have 1 independent variable in an experiment, but you can have many constants

5. Control Group
This is the group that you do NOTHING to. This group is left alone so that you can compare your experimental group to it.

6. For each of the following situations identify the variables

7. Students of different ages were given the same jigsaw puzzle to put together. They were timed to see how long it took to finish the puzzle.

8. Identify the variables in this investigation.

9. What was the independent variable?
Ages of the students
Different ages were tested by the scientist

10. What was the dependent variable?
The time it took to put the puzzle together
The time was observed and measured by the scientist

11. What was a constant? Same puzzle
All of the participants were tested with the same puzzle.
It would not have been a fair test if some had an easy 30 piece puzzle and some had a harder 500 piece puzzle.

12. Another example:

13. An investigation was done with an electromagnetic system made from a battery and wire wrapped around a nail. Different sizes of nails were used. The number of paper clips the electromagnet could pick up was measured.

14. What are the variables in this investigation?

15. Independent variable:
Sizes of nails
These were changed by the scientist

16. Number of paper clips picked up
Dependent variable:
Number of paper clips picked up
The number of paper clips observed and counted (measured)

17. Battery, wire, type of nail
Constants:
Battery, wire, type of nail
None of these items were changed

18. Another One:

19. The higher the temperature of water, the faster an egg will boil.

20. Independent variable – temperature of water
Dependent variable – time to cook an egg
Constants – type of egg

21. Last one:

22. The temperature of water was measured at different depths of a pond.

23. Independent variable – depth of the water
Dependent variable – temperature
Constants – thermometer

24. Designing Investigations

25. The greater the amount of soap in a soap and water mixture, the bigger a soap bubble can be blown.
Design an investigation to test this hypothesis.
Identify the variables
What exactly will be changed? How will it be changed?
What exactly will be measured? How will it be measured?
Explain in detail how you will conduct this experiment.

26. The farther a ball drops, the higher it will bounce.
Design an investigation to test this hypothesis.
Identify the variables
What exactly will be changed? How will it be changed?
What exactly will be measured? How will it be measured?